1. Field of the Invention
This invention relates to musical instrument pickups and, more particularly, to methods of characterizing, correlating and predicting pickup performance to thereby design and construct musical instrument pickups with a predictable tonal response. Accordingly, the general objects of the invention are to provide novel systems, methods, apparatus and models of such character.
2. Description of the Related Art
Certain musical instruments, especially electric guitars and other electric stringed instruments, use magnetic transducers to convert mechanical string vibrations into electrical signals that are subsequently amplified and fed into a loudspeaker. A musician typically selects musical instrument electronic components from a wide variety of options to achieve a particular musician-desired tonal quality. Tonal quality is important as it imparts an expressive element from a musician to a listener. For example, a guitar player may prefer analog circuitry over digital circuitry to achieve a more “vintage” tone. A guitar player's tone is directly related to the selection of desired amplifiers, guitars, and pickups (in addition to the playing style, finger pressure, etc., of the guitar player). With respect to guitar pickups, many factors, such as the number of coil winds, wire types, magnets, pole piece material, etc., are known to affect the tonal qualities of the pickup.
Many electric guitars use single-coil pickups. A significant and persistent drawback to traditional single coil pickups is noise. Due to their lack of active or effective passive noise reduction, single coil pickups are plagued by the fact that they tend to produce large amounts of background noise due to their tendency to pickup and transmit ambient electromagnetic signals, especially at higher gain amplification settings. This significant drawback of single coils pickups has inspired pickup designs that are intended to mimic the tonal characteristics of traditional single coil pickups while providing reduced noise levels. Such pickups are manufactured and/or marketed by a number of companies including; Fender® Musical Instrument Company, Kinman®, Lace® Sensor, DiMarzio®, Seymour Duncan®, Lindy Fralin® and others.
In reference to pickups designed to be direct replacements to traditional single coil pickups for the Fender® Stratocaster® and similar designs, many attempt to follow the basic dimensions of a traditional pickup. One popular design utilizes “stacked” coils, where the overall coil height (in the direction perpendicular to the longitudinal axis of the string) and width (along the longitudinal axis of the string) are similar or identical to a traditional pickup. Instead of a single coil, two coils are utilized, one “stacked” above the other, with the two coils incorporating opposite winding direction, and opposite magnetic orientation with respect to each other. In this way, the stacked coils are reverse-wound/reverse-polarity relative to each other and act to cancel noise while maintaining signal integrity, much as a “humbucking” pickup does. In these stacked designs, great pains can be taken to “tweak” the design parameters (wire size and type, number of turns, magnetic strength, etc.) in order to match the tone of a traditional single coil pickup as closely as possible. Stacked designs are marketed by Kinman® and DiMarzio® among others.
Other designs, such as the Seymour Duncan® Duckbucker®, use two coils; one for strings 1-3 and a second for strings 4-6. The coils are aligned at a constant angle relative to the longitudinal axis of the string, but are offset relative to each other with respect to the longitudinal axis of the string. This type of approach can be designed to fit into a traditional single coil space (such as the Duckbucker®) or the same approach can be designed to fit into a traditional Gibson® humbucker sized package (such as the Seymour Duncan® Twangbanger® or custom shop “3+3” series of offerings). In a recent market entry, Lindy Fralin® has developed a “split blade” design, where a projection of the blade pole piece overlaps the space between the 3rd and 4th (G and D, respectively) strings in an attempt to minimize the signal loss in this region.
While some of these approaches have enjoyed commercial success, there is still a feeling among many guitarists that they do not quite match the tonal characteristics of a traditional single coil pickup. It should also be noted that all of the designs intended to directly replace traditional single coil pickups must, by definition, fit into the same form factor and utilize the same mounting dimensions as their traditional counterparts as much as possible.
In fact, while the process of designing and manufacturing a high quality pickup remains as much of an art as a science, many of the designs follow the dimensions and electro-magnetic coupling patterns of their traditional counterparts as much as possible. This is at least in part because conventional thought in the art steadfastly posits that geometric concerns such as the orientation of the windings relative to the magnetic field and the vibrating string are critical to achieving a similar tone. For example, the stacked designs where the lower coil is typically a “noise sensing” coil are perceived to be tonally inferior to standard single coil designs, presumably due to the tone affecting properties of the subservient lower coil. As another example, Lindy Fralin's split blade design diverges from traditional design in incorporating continuous blade pole pieces rather than the discrete cylindrical pole pieces incorporated in standard designs. These design changes are viewed as necessarily resulting in tonal characteristics that are distinct from traditional single coil pickups.
Another single coil design is the “P90” pickup. P90 pickups are also prone to noise issues. A P90 pickup is basically a single coil with a different aspect ratio compared to a typical single coil pickup as utilized on a Fender® Stratocaster. The P90 coil is typically shorter than a Stratocaster® coil (i.e. in the direction parallel to the pole piece and perpendicular to the string axis) and wider in terms of the aperture it presents to the vibrating string (i.e. the direction perpendicular to the pole piece and parallel to the string axis). The P90 therefore senses the string vibration over more of the length of the string compared to a typical Stratocaster® single coil pickup. In addition, the P90 typically utilizes a magnetically susceptible pole piece (typically a steel screw) rather than a permanently magnetic pole piece. The magnetic field in P90 pickups is typically supplied by rectangular plate magnets positioned at the base of the pickup and in proximity to the screw pole pieces. There is a “staple” design P90 style pickup that does utilize permanently magnetic pole pieces.
Some designs have emerged to combat P90 noise. These designs are based on a very old design introduced by the Gibson® guitar company for the EBO bass guitar. Rather than a single coil, these designs utilize two coils positioned transversely, such that a permanent magnet is positioned in the center of each coil. The magnets are still positioned in proximity to the pole pieces similar to the traditional design (although the magnets would generally be closer to the vibrating string as they are no longer at the base of the pickup) but the coils themselves are rotated 90 degrees with respect to the long axis of the string. This results in a fundamental change in the way the vibrating string signal is coupled into the pickup and would ultimately have a different tonal signature compared to a traditional P90 pickup.
In another attempt to reduce single coil noise, “dummy coils” have been utilized to provide basically an antenna designed to capture noise of the same magnitude but opposite phase as the noise associated with the pickup while minimizing the tonal interference from the dummy coil. This system is manufactured by Suhr (the Backplate Silent Single Coil or “BPSSC” system) and as of this writing, it retails for on the order of $250. As a comparison a set of 3 new high quality traditional single coil pickups retails for about $190 (Fender® Custom Shop Pickups) to $240 (Lollar hand wound “boutique” pickups). This would indicate that some guitar players are willing to pay more than double the cost of pickups alone (not including installation) to achieve a traditional single coil guitar tone with reduced noise.
In U.S. Pat. Nos. 7,612,282 and 7,989,690 embodiments and methods for, inter alia, reducing the hum but still maintaining the tonal characteristics and basic dimensions of traditional single coil pickups were disclosed. The pickups disclosed in U.S. Pat. Nos. 7,612,282 and 7,989,690 provide significant noise reduction (compared to traditional pickups) while maintaining the basic tonal characteristics associated with the traditional pickup. There are two primary reasons for this: 1) all coils are active in the sensing and generation of signal (i.e. there are no dummy or secondary coils whose primary function is to cancel noise signal but not contribute substantially to the generation of string signal) and 2) the overall geometry and configuration of the coil arrangement and magnetic field of the traditional pickup is maintained. One design consideration of this style of pickup is the importance of presenting a consistent magnetic field across all strings.
Other multiple coil guitar pickup configurations have been taught, but an exhaustive review of the literature will not be given here.
The quality and applicability of a guitar pickup is defined by the tonal quality that it imparts on the note. Much of the process of designing a pickup is done empirically, and even that using minimal deviations from traditional materials and designs for the most part. Traditionally, a limited range of materials has been used in the majority of electric guitar pickup design and construction. Very little work has been done to quantify basic pickup electrical response and tie it to tonal performance. The effect of material properties on pickup performance, while recognized as important, has been very poorly and incompletely understood. To date the only known exceptions to the above noted general rule are the work of Helmuth E.W. Lemme, and Prof Steven Errede at the Univ. of Illinois to measure and characterize electric guitar pickup frequency response. Specifically, Lemme and Errede analyze pickup output, gain or impedance as a function of frequency and to graphically represent the same using rudimentary Bode plots. Their work, however, falls far short of the sophistication necessary to accurately capture the essence of the surprisingly complex nature of guitar pickups.